Optical Properties of a Liquid-Crystalline Random Copolyester

We have investigated the optical properties of Vectra A910, a commercially produced liquid-crystalline copolyester consisting of 4-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid subunits. The polymer is highly fluorescent in the near UV with an emission maximum at 428 nm (2.90 eV) and an excitation maximum at 376 nm (2.66 eV). The time-resolved fluorescent decays at room temperature were found to fit stretched exponential decays. Furthermore, the fluorescence kinetics were found to be highly dependent upon the emission wavelength. These results are consistent with the disorder from the random nature of the copolymer.